Apparatus for regulating the upper surface contour of expanded cellular products

ABSTRACT

Control of upper contour of foamed materials formed in an open top mold by selective control of lateral pressure to the rising foam and a conveyor type molding apparatus for achieving this control in continuous production.

United States Patent Ferstenberg 1 June 27, 1972 APPARATUS FORREGULATING THE UPPER SURFACE CONTOUR OF EXPANDED CELLULAR PRODUCTSInventor: Charles Ferslenberg, Paramus, NJ.

Assignee: Tenneco Chemicals, Inc., New York, NY. Filed: April 27, 1970Appl. No.: 41,659

Related US. Application Data Division of Ser. No. 750,034, Aug. 5, 1968,Pat. No. 3,560,599.

US. Cl ..425/364, 425/89, 425/4,

425/817 Int. Cl. ..B29f 1/00 Field of Search ..18/4 B, 4 S

[56] References Cited UNITED STATES PATENTS 2,921,346 l/l960 Fischer 18/4 B X 3,296,658 1/1967 Buffet a1... ..18/4 B 3,488,800 1/1970 Kornylak..l8/4 B FOREIGN PATENTS OR APPLICATIONS 1,044,321 1966 Great Britain..18/4 B Primary E.\'aminerH. A. Kilby, Jr.

Attorney Henry T. Burke, Robert Scobey, Robert S. Dunham, P. E.l-Ienninger, Lester W. Clark, Gerald W. Griffin. Thomas F. Moran, R.Bradlee Boal and C. C. Dunham [5 7] ABSTRACT Control of upper contour offoamed materials formed in an open top mold by selective control oflateral pressure to the rising foam and a conveyor type moldingapparatus for achieving this control in continuous production.

4 Claims, 8 Drawing Figures PATENTEB JUH 2 7 1972 SHEET 10F 2PATEr-HEDJmm m2 3, 672,348

SHEET 2 0F 2 llHll 111ml APPARATUS FOR REGULATING THE UPPER SURFACECONTOUR OF EXPANDED CELLULAR PRODUCTS This application is a divisionalapplication of U.S. patent application Ser. No. 750,034, now US. Pat.No. 3,560,599.

This invention relates to the manufacture of expanded cellular productsand more particularly it concerns novel arrangements for controlling theouter contour of such products. I

The present invention is particularly useful in connection with theproduction of continuous slats or blocks of foamed polyurethane materialfrom a liquid reaction mixture. These blocks are generally formed bypouring the liquid reaction mixture into an open top mold and allowingthe mixture to foam and rise, and eventually to solidify in the mold.This process may be carried out continuously in a very effective mannerby constructing the mold in the configuration of an endless or loop typeconveyor which moves continuously past and away from the liquid pouringpoint. When the liquid reac tion mixture is poured onto theconveyor-mold it undergoes the foaming and solidifying reactions whileit is being supported in proper contour and at the same time is beingcarried away from the pouring point. Thus, the liquid reaction mixturemay be poured continuously at the pouring point so long as theconveyor-mold is moving at proper speed.

A problem has long existed in connection with the use of open top moldsfor forming expanded cellular products. This problem involves thecontrol of the upper contour of the finished product. In general, theproduct will assume the mold contour in those regions where it contactsthe mold. However, in order to accomodate the rising foam and theevolution of gases therefrom, the upper portion of the molding apparatusis left open. Thus, there is no positive upper surface to control theupper contour of the rising foam.

It is a phenomenon of rising foams, such as polyurethane foams whichrise from liquid reaction mixtures to become selfsupporting expandedcellular products, that the natural rising action is greater in thecenter of the product than it is at the vertical sides. Accordingly,there is produced a crown-shaped or bulged upper surface. In general,the material in the crown has less commercial value than the remainderof the block,

mainly because of its shape.

The present'invention permits the formation, in an open top mold, of afoamed cellular product having a controlled upper contour which may, ifdesired, be flat. This controlled upper contour is achieved withoutundue difficulty or expense; and provides acommercially significantincrease in yield of prime quality foam per pound of reactants.

According to one aspect of the present invention, control of the topsurface contour of the foam is achieved by selectively altering theextent of foam rise across the horizontally transverse direction of thefoaming substance. This is achieved by exerting a horizontallytransverse compressive force on the vertical sides of the rising foam.

The present invention, in one aspect, makes use of the unusual abilityof solid or liquid foam material to absorb and dissipate compressivestresses. The novel results of this invention arise from our discoveryof a means of utilizing the unique behavior of such material. That is,contrary to the behavior of an essentially incompressible solid orconfined liquid, a foaming substance, that is not completely confined,particularly during the period of rising when it is still moldable, doesnot transmit uniformly throughout its mass and equalize appliedstresses. Thus, byimposing a laterally-directed compressive stress atthe sides of the foaming substance, a pressure variation is set upacross the transverse direction of the rising substance which isrelieved by the greatest proportionate upward movement of the portionsof the foam subjected to the greatest compressive stress, i.e. along thesides of the rising foam. Upward movement occurs along the sides of therising foam because this is the direction of least resistance to flow ofthe rising foam that is subjected to the lateral compressive stresses,thereby producing a flattened top surface contour in the rising foam.Dissipation of that component of the transversely applied stress whichacts in the machine direction of movement of the rising foam does notadversely affect achievementof the desired formation of a flat topsurface contour.

According to a further aspect of the present invention. there isprovided a novel conveyor type molding apparatus which is capable ofapplying horizontally transverse compressive stress in a selectivemanner to the vertical sides of rising foam con' tained therein, therebyto alter the foam rise pattern and more particularly its top surfacecontour according to a predetermined pattern. This novel conveyor typemolding apparatus of the present invention, contrary to prior conveyortype molding devices which have parallel side walls throughout theirlength, actually employs a transition region wherein the sidewalls ofthe conveyor taper in toward or out away from each other. The particularcontour, extent, length and location of the tapered transition regioncan be adjusted or established according to the desired final uppercontour, the chemical and physical nature of the rising foam material,and other conditions affecting the foaming process.

The tapered side walls of the conveyor mold apparatus may be stationary,or, as illustratively embodied herein, they may be movable at the samespeed as that of the foaming material itself. Moreover, the side wallsin the tapered transition may be hinged or swivelled at two or morepoints so that the contour itself of the taper may be adjusted. Theopposing side walls in the regions preceding and following the taperedtransition region are substantially parallel to the longitudinal centerline of the device.

According to still further aspect of the present invention, the extentof foam rise along the sides of the rising foam mass also is controlledselectively and aided by reducing the frictional resistance to foam risealong the vertical sides of the rising foam in a novel manner. This isachieved by allowing the side walls of the foam carrier web to risealong with the foam as hereinafter described. More specifically, therising foam is contained within a flexible one-piece carrier web whichis supported in open-top container-like configuration in theconveyor-mold having a tapered transition region.

In the past, the techniques employed to overcome the vertical componentof frictional resistance to the foam rise action have required side wallcarrier webs that were separate from the bottom carrier web. This wasdone in order to permit the raising of the side wall carrier websrelative to the bottom web, or to permit the lowering of the bottomcarrier web relative to the side wall carrier webs.

In the present case, it has been found that the single piece carrier weboperating in a tapered transition region in a conveyor-mold will undergosuch configurational changes in cross-section that the height of theside wall portions relative to the bottom wall portion of the web willincrease. Thus, the sides of the rising foam experience an effectiveupward movement of the side wall portions of the web.

As will be seen in detail hereinafter, the side wall taper describedabove is accompanied by a change in bottom wall inclination, thisserving to permit configurational changes in carrier web cross-sectionwithout the production or wrinkles. The bottom wall portion will dropfor an inward side wall taper so.that the effective rise in side wallheight (relative to the bottom wall) is even further augmented.

Various further and more specific objects, features and advantages ofthe invention will appear from the description given below, taken inconnection with the accompanying drawings, illustrating by way ofexample a preferred form of the invention.

In the drawings:

FIG. 1 is a side elevational section view of a conveyor type moldingapparatus in which the present invention is embodied;

FIG. 2 is a plan view of the molding apparatus of FIG. 1;

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 1;

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 1;

FIG. 5 is a schematic illustration depicting in cross-section a risingfoam substance in a molding device;

FIG. 6 is a view similar to FIG. 5 illustrating the control of foam riseaccording to the present invention;

FIG. 7 is a fragmentary enlarged section view taken along line 7-7 ofFIG. 1; and

FIG. 8 is a fragmentary perspective view showing a side conveyorconstruction used in the embodiment of FIG. 1.

As shown in FIGS. 1 and 2, a liquid reaction mixture 10 is pouredcontinuously from a dispensing nozzle 12 into a continuously-movingconveyor-type molding apparatus 14.

The liquid reaction mixture 10 is a blend of substances known to thosefamiliar with the art. These substances, when brought together, reactfirst to form a rising foam and then to solidify into an expandedcellular product. In order to produce an expanded cellular polyurethaneproduct, for example, the reaction mixture 10 may comprise hydroxylatedpolyesters, polyethers or the like mixed with organic polyisocyanates,catalysts, such as amine catalysts and stabilizers These reactionmixture ingredients are brought together in a blending apparatus (notshown) immediately ahead of the nozzle 12 and are then distributeddirectly into the molding apparatus 14, at its upstream end. The mixture10 is carried along in the molding apparatus away from the nozzle 12;and during this movement, it undergoes reactions which cause it to riseas a foam l3 and thereafter to solidify as an expanded cellular product15.

As shown in FIGS. 3 and 4, the molding apparatus 14 is of rectangularcross-section; and it is open at the top to permit free rise of the foam13. As the liquid reaction mixture 10 proceeds along in the moldingapparatus 14 and rises as a foam 13 and solidifies into a product 15, itassumes the crosssectional configuration of the molding apparatus walls.

It will be noted in FIGS. 2, 3 and 4 that the width of the moldingapparatus 14 is not fixed as in conventional conveyor systems; butinstead it actually decreases in the downstream direction along atransition region 16 in which foam rise occurs. The purpose for thisinward taper is to alter the extent of rise of the foam selectivelyacross the width of the apparatus as previously described. Thistransverse alteration of the extent of rise, serves to control thefinished upper contour of the foamed product 15. The manner in whichthis occurs can be seen in the schematic views of FIGS. 5 and 6.

FIG. 5 shows in cross-section a foaming substance 18 as it rises in anopen-topped rectangularly cross-sectioned molding device 20 according toits natural rise pattern. The molding device 20 has a flat bottom 21 andflat upright sides 22. It will be noted in FIG. 5 that the upper surfaceof the substance 18 is crowned, with a high center region 23 and loweredge regions 24. This rise pattern is caused, at least in part, by thefrictional resistance to upward movement imposed on the rising foam bythe sides 22 ofthe molding device 20.

Turning now to FIG. 6, it will be seen that the sides 22 ofthe moldingdevice are movable laterally to squeeze inwardly on the foamingsubstance 18. This action produces a lateral stress or pressure on thesides of the substance, as indicated schematically by arrows P and P,.Now it has been found that rising foam which is incompletely confineddoes not transmit and equalize the compression forces applied to theside walls. Thus, as indicated by pressure contour lines 25 in FIG. 6,there is produced a pressure variation across the foaming substance 18.This pressure variation, moreover, follows a pattern according to whichthe pressure is toward the center and greatest toward the vertical sidesof the substance.

The effect of the production of a varying transverse pressure or stresspattern in the foaming substance is to alter its rise pattern. Thisoccurs because the foaming substance tends to rise most rapidly in theregion of greatest applied pressure in an effort to reduce, or at leastequalize, the pressure variation imposed on it. Rise in the verticaldirection follows the path of least resistance that will relieve thepressure. Consequently, by controlling and varying the laterally-appliedpressure at the side wall regions of the rising and foaming substance18, the extent of rise at the edges of the foaming substance can bealtered to match the extent of rise at its center. As a result, anessentially flat top surface contour 32 is produced.

As shown in FIGS. 1-4, the conveyor type molding ap paratus is made upofa bottom conveyor 40 and two side conveyors 42. Each of theseconveyors is of the linked slat type. That is, each conveyor is made upof a plurality of flat slats 44 which are linked together to formcontinuous loops. As can be best seen in FIGS. 3 and 4, each of theslats is provided with rollers 46 which protrude from each end and whichride in guide rails 48. The guide rails 48 are shaped to define the patheach conveyor is to follow.

FIG. 7 illustrates the manner in which the individual slats 44 of thevarious conveyors 40 and 42 are linked together. As can be seen, eachslat is bent back to provide a hook-like formation 50 along each of itslongitudinal edges. These hook-like formations 50 are interconnected bybrackets 52 of C-shaped cross-section. The brackets 52 link the slats 44together in a manner allowing limited pivotal movement. Also, asillustrated in FIG. 8, the side conveyor slats can, in this arrangement,move relative to each other by a limited amount in the longitudinaldirection, thereby permitting the side conveyors 42 to follow changes ininclination of the bottom conveyor 40.

As can be seen in FIG. 1, the bottom conveyor 40 extends under thedispensing nozzle 12 along a path slightly inclined from the horizontal.Thereafter, in the foam rise region 16, the bottom conveyor 40 extendsalong a sharper incline as indicated by the angle 0: (shown exaggeratedfor purposes of illustration) in FIG. 1. Beyond the region 16, thebottom conveyor 40 reverts to a more nearly horizontal inclination,parallel to the inclination of the bottom conveyor section that precededthe taper zone.

Turning now to FIG. 2, it will be seen that the two side conveyors 42extend over the bottom conveyor and are arranged parallel to each otherboth upstream and downstream of the foam rise region 16. Within the foamrise region the side conveyors 42 taper in toward each other asindicated by the angle In order to provide flexibility and adaptabilityto variations in reaction materials and molding conditions, theconveyors 40 and 42 are constructed to permit adjustment of theinclination and taper angles a and B, adjustment in the spacing betweenthe side conveyors 42, and adjustment in the longitudinal extent of theregion over which the angles a and B are maintained. It will beappreciated that the taper and inclination angles a and B need not beconstant through the region 16. They may, in fact, constitute severalangles which define any desired overall taper or inclination contour. Asshown in FIGS. 1 and 2, the conveyors extend about sprocket wheels 56which are driven by motor means (not shown). Similar intermediatesprocket wheels 58 may be provided. The various sprocket wheels are allpositionally adjustable (by means not shown), to alter the length andlongitudinal position of the taper zone, and to alter the taper zoneangle and contour.

A molding web 60 of paper or other sheet-like material having a surfacefinish which will release easily from the liquid reaction mixture 10 orits product 15, is drawn continually from a roll or other source (notshown); and is passed through the molding apparatus 14. The molding web60 is initially flat. However, as it approaches the upstream end of theconveyors 40 and 42, its edges 62 are bent upwardly so that in passinginto the upstream end of the molding apparatus 14, the web 60 assumes agenerally channel-shaped cross-sectional configuration as illustrated inFIG. 3. In this configuration, the web is carried along by the conveyors40 and 42 under the dispensing nozzle 12 and there receives the liquidreaction mixture 10. The moving web then transfers the mixture 10through the foam rise region 16 and on to the downstream end of thedevice.

As the web 60 passes through the tapered foam-rise region 16, the sideconveyors 42 squeeze inwardly in a lateral direction on the web 60 whilethe bottom portion of the web inclines downwardly a corresponding amountcausing an increase in the distance from its edges 62 to its bottomcentral portion. Hence, a portion of the carrier web which would in anordinary, parallel walled conveyor system, remain in contact with thebottom conveyor, is caused to move upwardly along the side conveyors. Itis in this region that the lateral-pressure and foam-rise controldescribed above takes place. The degree of taper angle a, and the lengthof the tapered foam rise region 16 is controlled so that this lateralpressure is applied to the rising foam in an amount and at a time suchthat it will serve to increase the rise along the vertical sides of thefoam to balance the rise along the center of the foam.

Beyond the tapered foam rise region 16, the side conveyors 42 maintainthe edges 62 of the web 60 parallel to each other until the reactionproduct is fully formed. Beyond this point, the product isself-supporting and the conveyors 40 and 42 diverge away from theproduct, leaving it and the web 60 free to be handled for furtherprocessing.

lt will be appreciated that the angle of inclination (a) of the bottomconveyor 40 in the foam rise region 16 is mathmetically related to theinward taper ([3) of the side conveyors 42. The amount of thisinclination is adjusted in accordance with lateral taper (B) of the sideconveyors 42 in this region. This serves to avoid wrinkling so that theweb 60 may provide a smooth continuous molding surface along itsinterior. The amount of inclination change can be properly related tothe degree of lateral taper according to known geometrical andmathematical relationships that show the path of a ray in 3 dimensions.

The present invention further serves to provide top surface contourcontrol for the rising foam by reducing the frictional effects betweenthe sides of the rising foam and the sides of the molding apparatus. Ascan be seen in FIGS. 3 and 4, as the carrier web 60 changes to anarrower width by the tapering effect of the side conveyors 42, its sidewalls 62 also rise, while the overall perimeter width of the web itselfthat isin contact with the foaming material remains the same. lnaddition, the level of the bottom wall portion drops in this region. Asa result, the effective height of the side wall portions, relative tothe bottom wall portion, increases so that the relative move mentbetween the foam and the web is reduced in these regions. Accordingly,the resistance to foam rise is also relieved and the side wall regionsof the foam rise as freely as the center thereof. As a result, the topsurface contour of the risen foam becomes more nearly flat.

It may be seen that as a natural consequence of the use of an inwardtapering zone in the region of foam rise, vertical relative motion ofthe side walls is achieved using a single channelshaped carrier webinstead of three separate carrier webs. The vertical upward motion ofthe single carrier web along the sidewalls matches the degree of inwardtaper that occurs in the foam rise zone. For example, if the side wallshave an inward taper of 6 inches on each side, the portion of thecarrier web that moves along the side walls will also rise 6 inchesvertically as the carrier web traverses the inward tapering foam risezone. Although the vertical upward motion of the portion of theone-piece carrier web that traverses the side walls of the tapered zoneis a natural consequence of the inward taper, best use of this effect,to achieve good guidance of the carrier web through the conveyor moldapparatus, is obtained by also introducing a downward tilt in the bottomof the carrier web conveyor which matches the amount of the inwardtaper; in the case just described this downward tilt would amount to 6inches over the length of the zone wherein the inward taper of the sideis caused to occur.

While the present invention has been described in connection with amoving conveyor, it will be appreciated that the principles andadvantages are also obtainable in a stationary conveyor mold of similarinternal mold configuration, through which the foaming material passes.The zone of inward taper of the side walls in any apparatus designedaccording to the basic concept of this invention, may be varied to matchthe length of the zone over which the foam rise occurs. This lengthvaries in accordance with the reactivity of the foaming reactantmixture, and with the speed of the conveyor mold apparatus, according toprinciples known to those familiar with the art. This foam rise regionmay vary in length from four up to 25 feet, but is most commonly in thelength range of 8 to 18 feet from the reaction mixture pour point. Overthe length of the inward tapering region the side walls of the conveyormold may come together by an amount that can be varied in accordancewith the reactivity of the foaming mixture and the degree offlat-topping desired. It has been found that this amount of taper ineach side wall may be varied from zero (e.g., where the conveyor sidewalls are parallel) up to about 16 inches over the length of the taperedside wall region selected. In general, however, the desired top surfacecontour control results may be obtained with a taper in each side walladjustable between 4 and 12 inches over the length of the tapered sidewall regions selected.

Although a certain specific embodiment of the invention is hereindisclosed for purposes of explanation, further modifications thereof,after study of this specification, will be apparent to those skilled inthe art to which the invention pertains. Reference should accordingly behad to the appended claims in determining the scope of the invention.

What is claimed and desired to be secured by Letters Patent 1. Apparatusfor forming an expanded cellular product having an essentially flat topsurface contour from a foamable liquid reaction mixture, said apparatuscomprising a conveyor type open top mold operable to transport afoamable liquid reaction mixture away from a dispensing nozzle, saidconveyor in cross-section providing a horizontally extending bottom andupstanding sides to contain said mixture said mold including means forcausing said sides to move progressively inwardly toward each otheralong a region downstream of said dispensing nozzle, and means forcausing a downward inclination in said horizontally extending bottom insaid region whereby a foaming reaction mixture carried by said apparatusfrom said nozzle is subjected to lateral squeezing in said region duringthe rising action of said mixture, and as a result of such lateralsqueezing and downward inclination the rise pattern of said mixture isaltered.

2. Apparatus as in claim 1 wherein said mold includes means to guide aweb of flexible sheet material longitudinally therethrough in the samecross-sectional configuration as said conveyor to contain said reactionmixture.

3. Apparatus as in claim 2 wherein said means to guide a web includes alaterally extending bottom support and upstanding side supports, saidside supports tapering inwardly toward each other along said region.

4. Apparatus as in claim 3 wherein said side supports extendsubstantially parallel to each other in advance of and beyond saidregion.

1. Apparatus for forming an expanded cellular product having anessentially flat top surface contour from a foamable liquid reactionmixture, said apParatus comprising a conveyor type open top moldoperable to transport a foamable liquid reaction mixture away from adispensing nozzle, said conveyor in cross-section providing ahorizontally extending bottom and upstanding sides to contain saidmixture said mold including means for causing said sides to moveprogressively inwardly toward each other along a region downstream ofsaid dispensing nozzle, and means for causing a downward inclination insaid horizontally extending bottom in said region whereby a foamingreaction mixture carried by said apparatus from said nozzle is subjectedto lateral squeezing in said region during the rising action of saidmixture, and as a result of such lateral squeezing and downwardinclination the rise pattern of said mixture is altered.
 2. Apparatus asin claim 1 wherein said mold includes means to guide a web of flexiblesheet material longitudinally therethrough in the same cross-sectionalconfiguration as said conveyor to contain said reaction mixture. 3.Apparatus as in claim 2 wherein said means to guide a web includes alaterally extending bottom support and upstanding side supports, saidside supports tapering inwardly toward each other along said region. 4.Apparatus as in claim 3 wherein said side supports extend substantiallyparallel to each other in advance of and beyond said region.